Frais T (2025) Diurnal Variation in Severe Depression- A Hypothesis for the Mechanism of Action. Ann Psychiatry Ment Health 13(2): 1206.

Depression is the leading cause of disability around the world [1]. William Styron was an American writer and essayist who suffered from severe depression SD. In his book Darkness Visable: A Memoir of Madness he records his experience of the illness. He wrote: “The pain of severe depression is quite unimaginable to those who have not suffered it, and it kills in many instances because its anguish can no longer be borne.” 20% of SD people commit suicide Research is ongoing in to the effectiveness of different types of treatment. SD is a complex illness involving a number of areas of the brain and its numerous neurological systems. Pharmaceutical treatments cannot adequately address every pathogenic mechanism that causes and maintains the main symptoms of SD consequently, treatment failures are commonplace. Diurnal variations is recognized by DSM-5 and NICE guidelines but is not commonly listed as a symptom of SD in the various websites and books that offer information and advice for patients despite it being recognized that it is a meaningful symptom and that it is one of the defining features of SD [2,3].

There are two forms of diurnal variations. SD symptoms are experienced in the morning but easing in the evening.Conversely, some SD people are symptom free in the morning but suffer the full symptoms in the evening. It has been asserted that diurnal variations indicate that SD is biological in nature [3]. Diurnal variations do not happen at a fixed time. There can be instances where symptoms disappear for a short time during the day prior to the evening relief. It has been noted that a SD episode is often characterised by frequent and seemingly random fluctuations of the diurnal variations [4]. Due to the heterogeneous nature of SD, some may experience a gradual easing of symptoms and others may experience an instantaneous relief. Diurnal variations could be described as a false recovery. When the person experiences this sudden return to being symptom free at some point in the day, they believe they have finally come out of their depression only to find that symptoms return the next day. There have been cases where a person can be symptom free for the entire day but with symptoms returning the next day. The effect of diurnal variations relieving symptoms that last for a whole day. Although this effect has not been mentioned in any published article, there is anecdotal evidence from SD people who have experienced this [5]. Diurnal variations also has an impact on memory. This is when there is a symptom free experience, the SD person completely forgets the misery suffered during the course of the day. There is a difference between the false recovery and the real recovery. The false recovery via diurnal variation is instigated subconsciously whereas the real recovery is more likely to be psychologically instigated by the triggering of positive thoughts and with that, the brain’s instant recognition that no positive thoughts and observations have been made since the onset of the depression. It has been suggested that diurnal variations can be better understood when considering that disturbed circadian function and rhythms is the factor that underpins how diurnal variations work. Circadian function is an internally created, biological activity that runs on a roughly 24-hour cycle. Circadian rhythm controls change in an organism’s body, mind, and behaviour. A number of studies have found that abnormal circadian rhythms are commonly present in patients with SD [6,7]. It has been suggested that people with abnormal circadian function and symptoms that are worse in the morning could be treated with light therapy [8,9]. However, the results of these and other studies in to the nature of diurnal variations and possible treatments only demonstrate that a deeper understanding of how diurnal variations actually work remains elusive.

Any relief from symptoms even if for a relatively short time is clearly beneficial. SD and especially those people who are treatment resistant would barely be able to suffer full blown symptoms for every waking hour. If it were so, life would be completely unbearable and cases of suicide would rise. With diurnal variations, it could be that there is a tipping point where the brain goes in to a protective mode by activating a certain form of the brains immune system in a positive way which gives temporary relief from the crippling symptoms. This protective mechanism stems from the actions of the subconscious mind so cannot be self-controlled. But does the brain have some kind of positive immune system? Numerous studies conclude that inflammation of the brains immune system can lead to a negative immune response and underpin a depressive episode [10,11]. However, one study has suggested that the brains immune system may have another job, combatting depression. It is thought that immune cells might be involved in defending our mental health in addition to defending against microbial intruders [12].Another study suggests that T cells may promote neuroprotective and anti-inflammatory functions [13].The blood-brain barrier also protects the brain from immune system attacks through multiple structural and functional mechanisms. One study concluded that that there is a belief that some immune-system-targeting drugs could be useful in reducing depressive symptoms [13]. An author of a study in to the brain’s immune system remarked: ‘What we’ve found is that there is indeed immune surveillance of the brain — it’s just happening outside the brain. Now that we know where it’s happening, that opens up lots of new possibilities for modulating the immune system [14].” However, the problem with diurnal variations is that it is via the actions of the subconscious. This would suggest that this action stems from the actions of different neurological systems other than the systems which are involved in SD. Consequently, studies that advocate ways to activate a positive immune system response to treat SD may have no affect on the activation of diurnal variations.

Because there is evidence that the brain does have its immune system, it is entirely possible that a particular positive immune system of the brain may well exist which instigates the actions of diurnal variation giving welcome relief from the symptoms of SD. As relief of SD symptoms via diurnal variation is instigated from the subconscious, it may not be possible to discover a treatment that might stimulate this particular system with the possibility that it might somehow extend the duration of being symptom free. This is not to say that future research might develop a way to stimulate the subconscious [15,16]. In closing, psychiatrists, doctors and other mental healthcare workers and researchers who conduct medical trials with SD patients need to be aware of the phenomenon of diurnal variation. If a SD patient sees a doctor or psychiatrist on an evening appointment, it is possible that the patient is experiencing evening diurnal variations and as such, may appear to be somewhat cheerful which masks the fact that they have experienced all the disabling symptoms of SD for most of the day.

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Diurnal variations have been established as a symptom of severe depression where a person experiences all symptoms of severe depression during the day and the symptoms magically disappear in the evening only to return the next day. This is the action of diurnal variations. There are a number of studies that attempt to offer an explanation of how this phenomenon works. Many studies believe that diurnal variations involve interactions between circadian rhythms and mood regulation. However, the mechanism of action of diurnal variations is still not well understood. A theory is presented of how and why diurnal variations functions; that it is activated by a specific part of the brains immune system.

• Diurnal variations; Severe depression; Circadian rhythms; Mood regulation.